Praxis: Picking up good vibrations

By Patty Rooks on October 12, 2019.

praxis@praxismh.ca@PraxisMedHat

I am quite excited about the upcoming holiday this weekend – Thanksgiving! What a great time of the year to sit back and reflect on what we are thankful for. I hope that everyone out there takes just a minute and is able to reflect on how lucky we are; especially for the little things that we often forget about or take for granted. Of course, a holiday weekend would not be complete without some science fun. Here is a little something to keep those young scientists busy. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– large red plastic drinking cup (or another colour of choice)

– thin butcher type string

– buttons

– sponges

– scissors

– water

– nail

Procedure

1. Take the cup and place it on a sturdy surface upside down. Using the nail, punch it gently through the cup. Do not force it too hard as you will just crack the cup. Make another hole straight across from the first hole.

2. Cut a piece of string about 30 cm long – longer is better, we can always trim it up.

3. Flip the cup right side up. Looking at the inside, thread the string through the first hole, up out and over and back down through the second hole. Your string will be on the INSIDE of the cup now. Tie it in a knot and leave the excess string dangling like a pendulum string out the bottom of the cup.

4. You did it correctly if when you hold the cup upside down, the string will be dangling out from the middle of the inside of the cup.

5. Using the scissors, cut a piece of sponge about 5 cm x 5 cm. Note: I like the sponge that is kind of thin and even a bit rubbery feeling for this experiment, not the soft, thick fluffy ones.

6. Have an adult help you poke a hole through the centre of the sponge with the scissors. Pull the string through this hole in the sponge.

7. Now, tie a large button onto the end of this piece of string. You want it to be like a stopper so the sponge will not pull off of the string.

8. Dip the piece of sponge in a bit of water and squeeze it out so it is just moist, not dripping wet.

9. Pull the sponge to the top of the string.

10. Wrap/fold the wet sponge around the top of the string.

11. Gently squeeze the sponge against the string as you move the sponge down the string using jerky movements. You will hear a sound that closely resembles what a turkey may sound like! Enjoy!

What is going on?

Although the sponge is wet, there is still enough friction caused between the sponge and the string allowing the string to vibrate. As you pull the sponge down the string, you will feel it skip and bounce down. This irregular touching on the string produces tiny taps that force the string’s molecules to move back and forth. The vibrating string strikes the molecules in the cup, and the cup’s molecules strike the air molecules causing them to move back and forth in rhythm with the cup and string. The sound is made louder because the inside of the cup acts like a megaphone that concentrates the soundwaves and sends them out in one direction.

Mark your calendars! The annual Praxis Family Science Olympics will be held on Oct. 26 at Medicine Hat College. Doors open at 10 a.m.-3 p.m. Hands-on science fun for all ages.

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. NOTE our NEW address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403-527-5365, email: praxis@praxismh.ca.

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